1. Field of the Invention
The present invention relates to a video output apparatus, a video output method, a program, and a storage medium. More particularly, the present invention relates to a technique useful for saving power of a multi display system.
2. Description of the Related Art
Conventionally, there is a technique used in reducing power consumption of information processing terminals. According to this technique, power of a device connected to he information processing terminal is turned off according to its usage state, so that the power consumption can be reduced. In the information processing terminal, there is provided, for example, a timer for measuring a time period that the device connected to the information processing terminal is used. When the device is not used, the timer counts up. If the device is unused for a certain period of time and a count value of the timer reaches a certain value, the power of the corresponding device is turned off, so that power consumption is reduced.
Such a power management system is widely known as a standard such as Advanced Configuration and Power Interface (ACPI) in personal computers (PC). According to devices such as a personal computer, an operating system (OS), and a hardware device conforming to such power management standard, power of devices can be managed by the OS, and power consumption can be reduced accordingly.
On the other hand, in recent years, according to development of multi-screen, high-brightness, and large-size displays, power used for operating displays is increasing. Conventionally, there is a power saving technique for a single display or a multi display unit that monitors an operation of a device such as a keyboard or a mouse. If input from such a device is not detected for a certain period of time, the power supplied to the display is turned off. Such a technique is included in a function of a general operating system.
Japanese Patent Application Laid-Open No. 2001-350549 discusses a technique for changing a power state of a multi display unit to a state that is more adapted to the actual use state. Regarding a multi display system according to the technique discussed in Japanese Patent Application Laid-Open No. 2001-350549, a user face on the display is captured as video data. Then, which display that the user directs his or her look toward is determined from the video data. According to this determination, only the power of the display which the user is looking is turned on and other displays will be turned off. As a result, the display which is actually used is turned on and the power of the multi display system can be reduced.
As another technique, Japanese Patent Application Laid-Open No. 2000-163035 discusses a technique for managing individual power source of each display included in a multi display unit. According to the multi display system discussed in Japanese Patent Application Laid-Open No. 2000-163035, a display including a resource, such as an active mouse pointer or an active window, among a plurality of displays is monitored using resource information, such as a position of the mouse pointer or an active window. Then, when the resource is not displayed on a certain display for a certain period of time, the display is changed to a low power consumption mode. Accordingly, only the power of the display on which the user is actually using the mouse pointer or the display including the active window is turned on among a plurality of displays, and power for the other displays can be saved.
As described above, according to the techniques related to power saving of a multi display, the display the user is actually using is assumed by detecting, for example, the user's line of sight, the position of the mouse pointer, or the position of the active window, and power of each display is managed individually.
However, according to the above described techniques, one or more displays among a plurality of displays will be in a non-display state. Thus, it is difficult for the user to comprehend what has been displayed and which display the user desires to use has been displayed before the power saving is performed at sight. As a result, the user needs to turn on all the displays to find out which display has the window the user desires to use. This takes unnecessary time and effort.
Further, even if the multi display system is used, a display area of the window currently used may be small depending on arrangement of the window. For example, if relatively small windows are scattered over two screens of a multi display unit, the total area of these windows may be smaller than the area of one screen. In this case, although the windows can be displayed on one screen, since they are displayed using two screens, unnecessary power is used. Generally, since the position and size of a window the user uses depend on an operation by the user, it is assumed that the unnecessary power is often used as described above.
As described above, when the power of the display unit is managed by monitoring the operation of the devices such as a keyboard or a mouse, the power of a plurality of display units is collectively managed. Thus, if there is no input from such a device for a certain period of time, all the displays will be in a non-display state, and the user will not be able to see an object on the display that the user desires to see. Further, when the total area of the windows displayed on the screen of the multi display unit is small, all the display units will be in a non-display state due to power saving reasons. Even if the user desires to arrange the windows in a smaller number of display devices, since the power of each display cannot be individually managed, the power of each display device cannot be turned off. Accordingly, power saving cannot be performed.
Further, according to the technique discussed in Japanese Patent Application Laid-Open No. 2001-350549, one or more displays among a plurality of displays to which the user's line of sight is not directed will be in a non-display state for power saving reasons. Thus, it is difficult for the user to know the window that has been displayed before the power saving. Further, when a window that the user newly opens is arranged on a screen of a display in the non-display state, the user cannot quickly determine a display on which the new window is displayed. Thus, the user needs to direct his eye on all the displays so that they are changed into the display state.
Further, even if the total area of the windows displayed on the screen of the multi display unit is small, the user needs to direct his line of sight to all the display devices to turn them on. Thus, power is not saved as intended.
Similarly, the technique discussed in the Japanese Patent Application Laid-Open No. 2000-163035 is not usable in determining which window has been displayed before the power saving is performed. Further, even if the total area of the windows displayed on the screen of the multi display unit is small, the user needs to display all the screens by using, for example, a mouse pointer to turn them on. Thus, power is not saved as intended.